940  
FXUS65 KBYZ 291632  
AFDBYZ  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE BILLINGS MT  
1032 AM MDT THU JUL 29 2021  
   
UPDATE
 
 
QUICK UPDATE THIS MORNING TO ADJUST POPS TO CURRENT TRENDS.  
SCATTERED SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS HAVE BEEN  
MOVING THROUGH SOUTHERN AND EASTERN AREAS. SOME AREAS OF SHERIDAN  
COUNTY HAVE SEEN 0.50 TO ALMOST 0.75 INCHES OF WELCOME RAINFALL. STILL  
EXPECT ADDITIONAL SHOWER AND THUNDERSTORM DEVELOPMENT THIS  
AFTERNOON OVER WESTERN AREAS, SPREADING EAST THROUGH THE EVENING.  
THE REST OF THE FORECAST REMAINS ON TRACK AND THE PREVIOUS  
DISCUSSION IS BELOW. STP  
 

 
   
DISCUSSION
 
 
TODAY THROUGH FRIDAY NIGHT...  
 
UPPER RIDGE CENTERED OVER THE CENTRAL PLAINS WILL DOMINATE THE  
WEATHER OVER OUR REGION DURING THIS PERIOD WITH WARM CONDITIONS  
AND APPRECIABLE MOISTURE ALOFT. WEAK DISTURBANCES MOVING ALONG THE  
PERIPHERY OF THE UPPER RIDGE CAN PRODUCE ISOLATED TO SCATTERED  
SHOWERS AND THUNDERSTORMS OVER THE REGION TODAY AND OVER AREAS  
SOUTH AND WEST OF BILLINGS ON FRIDAY. PRECIPITABLE WATER VALUES  
TODAY WILL BE AROUND 1.0 TO 1.5 INCHES, WHICH IS THE 99+TH  
PERCENTILE FOR THIS TIME OF YEAR. STORM MOTION IS PROJECTED TO BE  
VERY SLOW, SO ANY STORMS WILL BE CAPABLE OF PRODUCING HEAVY  
RAINFALL FROM THE PLENTIFUL MOISTURE ALOFT AND SLOW STORM MOTION.  
TONIGHT INTO FRIDAY MORNING, A WEAK FRONT WILL MOVE EASTWARD OVER  
THE AREA AND MID-LEVEL WINDS WILL TURN NORTHERLY. THESE NORTHERLY  
WINDS WILL CAUSE DRIER AIR TO MOVE IN AND PRECIPITABLE WATER  
VALUES TO DROP TO NEAR 1.0 INCH ON FRIDAY, SO RELATIVELY DRIER  
CONDITIONS BUT STILL INDICATIVE OF HEAVY RAIN POSSIBLE FROM ANY  
SHOWERS/STORMS IN THE MOUNTAINS AND NEAR THE MT/WY BORDER. IF  
HEAVY RAIN OCCURS OVER THE BURN SCARS THAT WE HAVE SCATTERED ABOUT  
SOUTHERN MT AND NORTHERN WY, FLASH FLOODING IS POSSIBLE.  
 
IN TERMS OF SKY COVER...TODAY WILL BE MOSTLY CLOUDY WITH SMOKE  
FROM ONGOING FIRES IN THE REGION. CLOUD COVER WILL BE LESS ON  
FRIDAY BUT THERE WILL STILL BE SMOKE OVER THE REGION.  
 
HIGH TEMPERATURES WILL GENERALLY BE IN THE 80S TO LOWER 90S TODAY  
AND 90S FRIDAY. LOW TEMPERATURES WILL GENERALLY BE IN THE 50S AND  
60S TONIGHT AND FRIDAY NIGHT. RMS  
 
SATURDAY THROUGH NEXT THURSDAY...  
 
MODELS CONTINUE TO SHOW ORIENTATION OF UPPER LEVEL RIDGE  
STRETCHED NW TO SE ACROSS THE REGION TO START THE PERIOD. THIS  
LOOKS TO KEEP MONSOONAL MOISTURE OFF TO THE SOUTH AND WEST THROUGH  
THE WEEKEND, KEEPING ANY PRECIP POTENTIAL MAINLY CONFINED TO THE  
HIGH TERRAIN. SOME ACTIVITY MAY BE ABLE TO MOVE OFF THE TERRAIN,  
BUT HIGH PRESSURE WILL LIMIT THAT SIGNIFICANTLY.  
 
A STRONG WAVE WILL PUSH EASTWARD SUNDAY EVENING/NIGHT, FORCING  
RIDGE AXIS EASTWARD, AND BEGIN FLATTENING THE RIDGE. THIS WAVE  
WILL BRING STORMS TO THE HIGH TERRAIN MUCH OF THE MONDAY, WITH  
STORMS SPREADING EASTWARD TO BILLINGS BY MONDAY EVENING. THIS WAVE  
WILL CONTINUE SHIFTING EASTWARD OVERNIGHT, BRINGING SHOWERS AND  
THUNDER ACROSS THE REGION THROUGH TUESDAY, AS IS FULLY FLATTENS  
THE RIDGE.  
 
FLOW REMAINS FLAT AND PROGRESSIVE THROUGH THE REMAINDER OF THE  
FORECAST PERIOD, WITH DAILY AFTERNOON/EVENING SHOWER/THUNDER  
POTENTIAL  
 
TEMPERATURES WILL CONTINUE TO BE HOT, WITH 90S COMMON ACROSS MOST  
OF THE REGION. NEAR MOUNTAIN REGIONS WILL LIKELY SEE MORE MID TO  
UPPER 80S, WITH MORE EXTENSIVE CLOUD COVER. GILSTAD  
 

 
   
AVIATION
 
 
SCATTERED SHOWERS CONTINUE ACROSS SOUTHERN ROUTES THIS MORNING,  
BUT DO NOT EXPECT ANY SIGNIFICANT AVIATION CONCERNS, AS ACTIVITY  
ARE FAIRLY HIGH BASED. THEREFORE, MAINLY VFR CONDITIONS WILL  
PREVAIL.  
 
ADDITIONAL SCATTERED THUNDERSTORMS ARE EXPECTED THIS  
AFTERNOON/EVENING. LOCALIZED HEAVY RAINFALL IS POSSIBLE WITH THESE  
STORMS, WITH POSSIBLE REDUCTION OF FLIGHT CONDITIONS TO MVFR. GUSTY  
SURFACE WINDS ARE ALSO POSSIBLE THIS AFTERNOON AND EVENING,  
ESPECIALLY AROUND STORMS.  
 
SMOKE ALOFT WILL CONTINUE TO REDUCE SLANT RANGE VISIBILITY. SOME  
LOCATIONS NEAR THE FOOTHILLS MAY SEE SURFACE VISIBILITY REDUCED TO  
MVFR AT TIMES DUE TO SMOKE. GILSTAD  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
TDY FRI SAT SUN MON TUE WED  
-------------------------------------------------------  
BIL 091 065/094 066/092 066/094 065/092 065/090 062/091  
3/T 21/U 11/U 01/B 13/T 44/T 32/T  
LVM 091 058/093 057/090 057/091 058/087 057/086 052/088  
5/T 32/T 12/T 13/T 36/T 55/T 33/T  
HDN 093 061/096 062/094 060/095 060/094 060/091 059/093  
4/T 31/U 11/U 01/B 12/T 33/T 22/T  
MLS 085 064/093 064/093 063/093 063/093 064/092 064/092  
4/T 31/U 00/U 00/U 01/B 22/T 22/T  
4BQ 089 064/088 063/091 060/090 062/092 063/088 062/090  
5/T 62/T 11/U 00/U 11/U 23/T 22/T  
BHK 086 060/090 060/091 057/091 058/091 061/090 061/091  
3/T 51/U 00/U 00/U 01/B 12/T 22/T  
SHR 090 059/089 059/087 055/089 057/090 057/086 056/089  
7/T 64/T 22/T 11/B 13/T 34/T 32/T  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
WY...NONE.  
 

 
 

 
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